Bacterial Dynamics in Large and Small Estuaries

We have been investigating bacterioplankton biomass and production in Chesapeake Bay for the past decade. More recently we initiated a system-level study of bacterial and DOM dynamics in the York River, Virginia, a small (100 km) subestuary of the Chesapeake Bay. In Chesapeake Bay, where water residence times are long (months), bacterial biomass and production show maxima in the middle, mesohaline reaches of the estuary. In contrast, in the York River bacterial rates and biomass consistently show opposing monotonic trends, with biomass increasing, and activity decreasing, to the seaward. Dissolved organic carbon (DOC) utilization experiments and natural carbon isotopic abundance data suggest that terrestrial DOC supplied in the freshwater inflow is used preferentially and may structure the bacterial community. The contrasting patterns within and between estuaries were analyzed with respect to the DOM supply hypothesis and other environmental controls, and compared to oceanic patterns.